Relatively costly methods exist for control of sulphur oxide pollution from fossil fuel-fired combustors, but they are most commonly applied to new facilities where the expense and control of the technology is justifiable due to the long remaining depreciable lifetime of the facility. There is a large population of older combustors in existence for which the cost-effective methods of reducing sulphur oxide emissions are not generally available due to the substantial additional capital expense which would need to be expended on an old facility. There is a need, therefore, to develop cost-efficient, retrofittable technology to control sulphur oxides and nitrogen oxides in this population of older plants.
In other methods, inorganic promoters have been added to each of the calcium-based sorbents in an effort to increase their reactivity. Promoters can increase reactivity significantly but each group of effective promoters has problems which preclude it from practical application. Transition metals such as chromium are effective in various forms but they are relatively expensive and may produce environmental side effects of their own. Alkali metal additives are aggressive promoters during natural gas-firing, but are condensed on the ash which is produced during coal-firing and are unavailable to promote SO.sub.2 capture by the sorbent. There remains a need in the art, therefore, for a sorbent with an improved capability of capturing SO.sub.2 that will not be depleted by ash interactions in a coal-fired combustor, and which does not introduce detrimental environmental effects.
It is thus an object of the present invention to provide a method for removing sulphur-containing gases, particularly sulphur oxides, from the exhausts of fossil fuel-fired combustors.
It is also an object of the present invention to provide an improved sorbent for removing sulphur oxides from the exhaust gases of fossil fuel-fired combustors when said sorbent is injected into, or downstream from the combustor.
These and other objects of the present invention will be apparent from the following description and appended claims.